1. Field of the Invention
The present invention relates to a method of driving DC plasma display panels, and more particularly, to a method of driving a DC plasma display panel according to a DC memory system wherein a compensation pulse for reducing the contamination of a displayed image taking place by the application of a write pulse is applied near the write pulse so that the apparent output of light-emission is reduced to eliminate the contamination phenomenon and also to reduce the generation of false outlines with respect to a displayed image.
2. Description of the Related Art
Conventionally, there have been proposed a DC plasma display panel driving method according to a pulse memory system wherein a sustain pulse is applied on a display anode in the connection diagram shown in FIG. 3 at a timing shown in the time chart in FIG. 4 and a DC plasma display panel driving method according to a DC mode memory system in which a write pulse is applied on a display anode at a timing shown in FIG. 5.
First, to describe the operation of the arrangement shown in FIGS. 3 and 4, reference numeral 11 designates a cathode bus, reference numeral 12 designates a scanning (auxiliary) anode bus and reference numeral 13 designates a display anode bus. Reference numeral 14 designates a scanning cell which is provided at each point of intersection of the cathode bus 11 and the scanning anode bus 12 and reference numeral 15 designates a display cell which is provided at each point of intersection of the cathode bus 11 and the display anode bus 13. Further, in each of the display cells 15 there is inserted in series a resistor 22 for discharge stabilization. In some methods, such series-connected resistor 22 is also inserted into each scanning cell 14 which, however, is omitted herein. Thus, a write pulse 17 is applied on the display anode bus 13 which is being applied with a maintenance pulse 16 and at the same time, a scanning pulse 18 and an erasing pulse 19 are applied on the cathode bus 11 to thereby display an image on a memory panel 20.
Further, when driving according to the DC memory mode in FIG. 5, a predetermined sustain voltage is applied on the display anode bus 13 and at the time of writing, a write pulse 21 is applied on the bus 13.
It is noted that the black-painted portions of the scanning cells and the display cells show that they are in the state of discharging.
Of the above-mentioned two conventional methods, the first method is disclosed in the Journal of the Institute of Television Engineers of Japan (April 1984, p. 332 by Murakami, et. al.) and the second method is described by the inventor of the present invention in his Ph.D. thesis entitled "A Study of Providing High Performance to the DC Discharge Type TV Display Panel" (Ph.D. Thesis, Tohoku University, February, 1994, p. 25).
Particularly, the second method of driving according to the DC mode memory system has had the drawback that the presence of the write pulse increases the discharge current of the cell which continues to discharge for maintenance, so that the brightness of the displayed image intensifies to cause a contamination phenomenon in the vertical direction to generate.
The present invention has been made in view of the above-described situation and an object of the present invention is to provide a method of driving DC plasma display panels which method is capable of eliminating the contamination of a displayed image in the vertical direction and making the displayed image clear and distinct.